Apparatus for casting windings in electric motor rotors



E. P. LARSH Sept, 27, 1960 APPARATUS FOR CASTING WINDINGS IN ELECTRICMOTOR ROTORS Filed April 25, 1958 EVERFTT R LARBH ATTORNEYS APPARATUSFOR CASTING WINDINGS IN ELECTRIC MOTOR ROTORS Everett P. Larsh, 124 E.Monument Ave., Dayton, Ohio Filed Apr. 25, 1958, Ser. No. 730,918 2Claims. (Cl. 22116) This invention relates to electric motor rotors andin particular to a method and apparatus for casting windings in therotors of squirrel cage motors.

A large class of electric motors utilizes a rotor consisting of amagnetic frame and a squirrel cage or amortisseur winding thereon. Sucha winding consists of a plurality of spaced bars extending axial-1ythrough the rotor and connected at the ends of the rotor by conductiveend rings. These bars are often inserted in the slots of the rotor andthe end rings applied thereto by riveting or welding, but a prefer-redmanner of supplying the winding to the rotor is to cast the windingdirectly into the slots of the rotor while simultaneously forming theend rings on the rotor, all as a single integral casting.

Some difficulty has been experienced in obtaining sufficiently densecastings in such cases to make all of the rotors absolutely uniform asto their electrical characteristics; and there has further resultedconsiderable difficulty with the cast material being smeared about the Astill further object of this invention is the provision' of a method andapparatus for casting windings in electric motor rotors which is adaptedfor being incorporated in an automatic machine thereby leading toextremely rapid production of the rotors.

A still further object of this invention is the provision of a methodand apparatus for casting windings in electric motor rotors in which aminimum amount of time is required for the cast winding to commencesetting up in the rotor thereby permitting the rotors to be processedextremely rapidly through the casting machine.

These and other objects and advantages will become more apparent uponreference to the accompanying drawings, in which:

Figure 1 is a perspective view showing a stack of rotor laminationspreparatory to the casting operation,

Figure 2 is a vertical sectional view taken through the apparatusaccording to this invention in which the windings are cast into therotor, Figure 3 is a fragmentary sectional view indicated by 'line 33 onFigure 2 but showing the rubberlike sleeve that surrounds the rotorexpanded into pressure engagement with the periphery of the rotor,

Figure 4 is a fragmentary view drawn at increased scale showinghow theflexible sleeve surrounding the rotor is pressed into the mouths of theslots of the rotor thereby preventing the casting metal from obstructingthe mouths of the slots thus providing for a clean pe1iphcry on therotor, and

tates Fatent O ice Figure 5 is a sectional perspective view showing therotor after the winding has beencast therein.

Referring to the drawings somewhat more n the stack of laminations inFigure l is generally indicated at 10 and consists of a plurality ofindividual laminations having slots 12 for receiving the windings to be'cast therein and with each slot, as illustrated, having a mouth.

14 although the slots may be closedif desired. A central bore 16 isprovided in the rotor for receiving the rotor supporting shaft which isplaced in the rotor after the windings have been cast therein.

Turning now to the apparatus in which the-winding is cast into therotor, this is shown in Figure 2 wherein it will be seen that there is abottom die part 18 which may be bolted into a turret or slide 20 so thatbottom die part 18 rests on a stationary base member 22. Base:

member 22 is provided with cylinder means 24 in which there isreciprocable an injection plunger 26. The space above plunger 26 at 28is adapted for receiving molten casting metal and this metal is forced,by upward movement of plunger 26, upwardly through the openings 30- inthe upper part of base member 22 and thence through openings 32 in thebottom of bottom die member 18 into cavity 34 in the said die member.

The apparatus of Figure 2 also comprises an upper die member 36 which issecured as bycap screws 38 toy-a.

vertically movable ram or support 39. The upper die member 36 is formedsimilarly to the lower die member and includes a cavity 40 correspondingto cavity 34 of J the lower die member and which cavity 40 communicatesvia passages 42 with a space 44 in ram 39.

The upper die member 36, according to the present invention, supports anannular member 46 that has therein an annular groove 48 closed towardthe center of member 46 by a sleeve 50. Member 46 also carries aresilient rubberlike sleeve 52, preferably of silicon rubber or otherflexible readily deformable heat resistant material. Sleeve 52 has itsopposite ends turned over the end parts of member 46 and secured theretoby the draw rings 54. This provides for a fluid tight connection betweensleeve 52 and member 46.

A fluid inlet pipe 58 controlled by a valve 60 extends through member 46and sleeve 50 so as to supply fluid to the space between sleeve 50 andrubberlike sleeve 52.

A fluid exhaust conduit 62 controlled by a valve 64 connects with therecess 48. Communication between opposite sides of sleeve 50 is had byports 66 which are preferably located in the sleeve on the side of theapparatus opposite fluid inlet pipe 58.

The upper die member 36 also has attached thereto a center post 68slightly longer than the stack of laminations into which the winding isto be cast and with there being provided a central bore 70 in the lowerdie member for receiving the lower end of the post.

In utilizing the apparatus, a stack of laminations of the right heightis assembled and these may be aligned with each other by bars insertedin the slots or by a keyway formed along bore 16. In any case, after thelamina tions have been stacked and aligned, they are placed on It willbe noted that both the upper and lower die members engage thelaminations adjacent the bore 16 in an annular region designated 72 andalso at an annular region designated 74 which is at the tips of theteeth of 5 In this manner the laminations are securely and tightlyclampedtogether so that when the casting the rotor.

detail,

metal is injected into the slots under pressure it will have little orno opportunity for flowing outwardly between the laminations even whereconsiderable pressure is employed.

The length of the member 46 is such that the die members will closeagainst the laminations under pressure and while at the same time atleast lightly engaging the opposite ends of the rubberlike sleeve 52.There may even be some clearance at the ends of the sleeve 52 because asupply of pressure through conduit 58 will be suflicient to expand thesleeve 52 into pressure engagement with the entire periphery of therotor and the upper and lower die members thereby tightly to seal thecavity into which the casting metal is to be forced.

When the stack of laminations is clamped in place as described, fluidunder pressure is. introduced through con-.

duit 58 to expand rubberlike sleeve 52 in the manner also describedabove. This fluid may be air under pressure but I prefer to employ aliquid such as Water and which liquid is circulated continuouslyeboutsleeve 52 thereby to have a cooling effect thereon. This is the reasonfor locating the ports 66 on the side of sleeve 50 opposite conduit 58.The pressure may be maintained about rubberlike sleeve 52 by supplyingliquid under pressure through conduit 58 while restricting the dischargeof the liquid through conduit 62 by adjustment of valve 64.

With the apparatus closed and the flexible sleeve 52 expanded asdescribed, plunger 26 is then thrust upwardly and the molten castingmetal is driven into the casting cavity to form the winding in therotor. The casting of the winding in the rotor may be accompanied by thesimultaneous forming on one or both of the end rings of the windings fanblades that will circulate air in the motor after it is completed. Suchfan blades may be formed merely by providing one or both of cavities 40and 34 with spaced axially extending partition members 73. Also, the fanblades may be provided with notches or recesses therein by providing theannular element 76 extending into the cavity in which the fan blades areformed. Such notches or recesses are useful for supporting switchactuators and the like on the end of the rotor. Notches or grooves ofthis nature could be provided in a solid end ring by the samearrangement, if desired.

It will be noted that the passages 42 at the upper end of the rotor areof small size and because of this the metal cast into the rotor willchill before it flows compeltely through the passages 42 thus preventingin most cases any metal from entering chamber 44.

Chamber 44 could have a suction drawn thereon through the member 39 forevacuating the space into which the metal is to be cast, if so desired,thereby increasing the speed with which the apparatus can be operatedand preventing the formation of air pockets in the casting andpermitting the metal to be introduced into the cavity with greater speedwhereby it can be rammed tight while still in a fairly fluid conditionthus providing for a dense high quality cast winding.

When the sleeve 52 is expanded by liquid pressure, the liquid acts as acoolant thus preventing the temperature of sleeve 52 from being raisedto a point where degeneration of the material of the sleeve commences totake place. The chilling effect of the liquid on the sleeve also bringsabout rapid setting of the metal in the mouths of the slots and becauseof this a somewhat higher metal temperature can be employed than withother devices and higher pressure ramming of the metal can be ernployed,all tending to produce better quality casting than has heretofore beenpossible.

Furthermore, the sleeve as illustrated in the present applicationtightly seals about the periphery of the rotor and also against the endmembers of the die even in the presence of foreign particles and againstirregular surfaces thereby preventing any flashing of the metal evenwhen driven into the casting cavity in a highly lluid state and underextremely high pressures.

The manner in which the relatively thin flexible rubberlike sleeve 52flows into the mouths of the slots is illustrated in Figures 3 and 4 andit will be seen that the rubberlike sleeve substantially confines themetal to the region of the slot proper and that the mouths of the slotsare substantially free of any casting metal. The exact amount that thecasting metal will be recessed below the periphery of the rotor can becontrolled by controlling the pressure supplied to the outside offlexible sleeve 52.

The rotor when the winding is cast therein according to the presentinvention can be cleaned up readily with a light turning or grindingoperation 'and there will be no casting material smeared about the rotoror dragged into the region between adjacent laminations, and thegrinding wheel, if the rotor is ground, will remain clean After themetal has been cast into the cavity and has set up sufficiently topermit retraction of plunger 26, a matter of only a few seconds, theplunger is moved downwardly, the supply of pressure through conduit 58is interrupted, and the upper die member together with member 46carrying flexible sleeve 52 is retracted upwardly. At this time, undernormal conditions, the rotor will remain on the lower die member due tothe casting metal that remains in the passages 30 in base member 22.This will strip the rotor from the upper die member so that the upperdie member is ready to be used with another stack of laminations.

The lower die member 18 is then moved away from casting position byactuating the turret or support member 20 and this is effective forshearing off the gates extending through the lower die member. Anotherlower die member at this time can be moved into casting position forreceiving a new stack of laminations, and the cycle is repeated.

It will be seen that the method and apparatus of the present inventionprovides for highly eflicient extremely rapid casting of windings intostacks of laminations and that the method and apparatus is particularlyadapted for use with automatic machines and that the casting condi tionsestablished are such that dense void free castings are produced thusleading to uniform electrical characteristics for the rotors which areso provided with windings.

It has been mentioned that the slots of the rotor may be closed aboutthe periphery of the rotor but even in this case it is necessary toenclose the rotor when the casting operation is carried out because thehigh pressure casting metal may flash out between the laminations orsome of the laminations may have faults therein at the outer extremitiesof the slots. It will be understood, therefore, that the presentinvention contemplates rotors of both types.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and conditions, andaccordingly, it is desired to comprehend such modifications within thisinvention as may fall with? in the scope of the appended claims.

I claim: 1. An apparatus for casting windings into the slots of a stackof laminations that form the magnetic core of an electric motor rotorwhich comprises; die members adapted for engaging opposite ends of thestack of laminations, an annular member surrounding the core and havingan annular cavity opening toward the core, an-

into sealing engagement with the periphery of the rotor, meansinterconnecting the chambers opposed from said one point and means forwithdrawing liquid from the outer chamber at the said one point so thatthe liquid cools the sleeve upon the introduction of molten castingmetal into said slots, the die members engaging the opposite ends of thestack of laminations in pressure engagement while allowing expansion ofsaid rubberlike sleeve into sealing engagement with the surface of therotor, and means for forcing molten casting metal into the annularcavity of one of said die members whence it flows through the said slotsinto the cavity of the other die member thereby forming an integral castwinding in the stack of laminations including end ring portions.

2. An apparatus for casting windings into the slots of a stack oflaminations that form the magnetic core of an electric motor rotor whichcomprises; die members adapted for engaging opposite ends of the stackof laminations, an annular member surrounding the core and having anannular cavity opening toward the core, annular cavities in said diemembers communicating with the ends of said slots, an annular membersurrounding the stack of laminations and comprising a thin, flexiblerubberlike sleeve, a second sleeve in the cavity dividing it into innerand outer chambers, means for introducing a liquid under pressure intothe inner chamber at one point of the annular cavity thereby to forcethe sleeve into sealing engagement with the periphery of the rotor,means interconnecting the chambers opposed from said one point and meansfor withdrawing liquid from the outer chamber at the said one point sothat the liquid cools the sleeve upon the introduction of molten castingmetal into said slots, the die members engaging the opposite ends of thestack of laminations in pressure engagement while allowing expansion ofsaid rubberlike sleeve into sealing engagement with the surface of therotor, said die members remaining in fixed position with respect to eachother during the expansion of said rubberlike sleeve, and means forforcing molten casting metal into the annular cavity of one of said diemembers whence it flows through the said slots into the cavity of theother die member thereby forming an integral cast winding in the stackof laminations including end ring portions.

References Cited in the file of this patent UNITED STATES PATENTS1,251,951 Ashdown Ian. 1, 1918 1,603,545 Johnson Oct. 19, 1926 2,192,787Elrey Mar. 5, 1940 2,289,929 Parker July 14, 1942 2,524,737 Sawyer Oct.3, 1950 2,781,565 Atchison Feb. 19, 1957 2,807,844 Hemphill -1 Oct. 1,1957

